<template>
	<canvas id="myCanvas"></canvas>
</template>

<script>
export default {
	name: "ribbons",
	props: {
		darkStyle: Boolean,
	},
	methods: {
		themeChange() {
			localStorage.setItem("darkTheme", this.darkStyle);
			let myCanvas = document.getElementById("myCanvas");
			if (this.darkStyle) {
				myCanvas.style["backgroundColor"] = "#1f1f1f";
			} else {
				myCanvas.style["backgroundColor"] = "#ffffff";
			}
		},
	},
	created() {
		this.$nextTick(() => {
			let darkStyle = localStorage.getItem("darkTheme") == "true";
			const myDate = new Date();
			if (
				!darkStyle &&
				(myDate.getHours() >= 22 || myDate.getHours() <= 6) // 夜间22:00至第二天早上7:00，将自动切换至深色模式
			) {
				darkStyle = true;
				this.$message({
					dangerouslyUseHTMLString: true,
					message:
						"<i class='el-icon-moon'></i>夜深了，系统已自动为您切换至深色模式。请爱护好自己的眼睛哦！<i class='el-icon-view'></i>",
					type: "",
					duration: 2000,
					showClose: false,
					center: true,
				});
			}
			this.$emit("update:darkStyle", darkStyle);
			let _w = window,
				_b = document.body,
				_d = document.documentElement;
			let random = function () {
				if (arguments.length === 1) {
					if (Array.isArray(arguments[0])) {
						let index = Math.round(
							random(0, arguments[0].length - 1)
						);
						return arguments[0][index];
					}
					return random(0, arguments[0]);
				} else if (arguments.length === 2) {
					return (
						Math.random() * (arguments[1] - arguments[0]) +
						arguments[0]
					);
				}
				return 0;
			};
			let screenInfo = function () {
				let width = Math.max(
						0,
						_w.innerWidth || _d.clientWidth || _b.clientWidth || 0
					),
					height = Math.max(
						0,
						_w.innerHeight ||
							_d.clientHeight ||
							_b.clientHeight ||
							0
					),
					scrollx =
						Math.max(
							0,
							_w.pageXOffset ||
								_d.scrollLeft ||
								_b.scrollLeft ||
								0
						) - (_d.clientLeft || 0),
					scrolly =
						Math.max(
							0,
							_w.pageYOffset || _d.scrollTop || _b.scrollTop || 0
						) - (_d.clientTop || 0);
				return {
					width: width,
					height: height,
					ratio: width / height,
					centerx: width / 2,
					centery: height / 2,
					scrollx: scrollx,
					scrolly: scrolly,
				};
			};
			let Point = function (x, y) {
				this.x = 0;
				this.y = 0;
				this.set(x, y);
			};
			Point.prototype = {
				constructor: Point,
				set: function (x, y) {
					this.x = x || 0;
					this.y = y || 0;
				},
				copy: function (point) {
					this.x = point.x || 0;
					this.y = point.y || 0;
					return this;
				},
				multiply: function (x, y) {
					this.x *= x || 1;
					this.y *= y || 1;
					return this;
				},
				divide: function (x, y) {
					this.x /= x || 1;
					this.y /= y || 1;
					return this;
				},
				add: function (x, y) {
					this.x += x || 0;
					this.y += y || 0;
					return this;
				},
				subtract: function (x, y) {
					this.x -= x || 0;
					this.y -= y || 0;
					return this;
				},
				clampX: function (min, max) {
					this.x = Math.max(min, Math.min(this.x, max));
					return this;
				},
				clampY: function (min, max) {
					this.y = Math.max(min, Math.min(this.y, max));
					return this;
				},
				flipX: function () {
					this.x *= -1;
					return this;
				},
				flipY: function () {
					this.y *= -1;
					return this;
				},
			};
			let Factory = function (options) {
				this._canvas = document.getElementById("myCanvas");
				this._context = null;
				this._sto = null;
				this._width = 0;
				this._height = 0;
				this._scroll = 0;
				this._ribbons = [];
				this._options = {
					colorSaturation: "80%",
					colorBrightness: "60%",
					colorAlpha: 0.65,
					colorCycleSpeed: 6,
					verticalPosition: "center",
					horizontalSpeed: 200,
					ribbonCount: 4,
					strokeSize: 0,
					parallaxAmount: -0.5,
					animateSections: true,
				};
				this._onDraw = this._onDraw.bind(this);
				this._onResize = this._onResize.bind(this);
				this._onScroll = this._onScroll.bind(this);
				this.setOptions(options);
				this.init();
			};
			Factory.prototype = {
				constructor: Factory,
				setOptions: () => {},
				init: function () {
					try {
						this._canvas.style["display"] = "block";
						this._canvas.style["position"] = "fixed";
						this._canvas.style["margin"] = "0";
						this._canvas.style["padding"] = "0";
						this._canvas.style["border"] = "0";
						this._canvas.style["outline"] = "0";
						this._canvas.style["left"] = "0";
						this._canvas.style["top"] = "0";
						this._canvas.style["width"] = "100%";
						this._canvas.style["height"] = "100%";
						this._canvas.style["z-index"] = "-1";
						if (darkStyle) {
							this._canvas.style["background-color"] = "#1f1f1f";
						} else {
							this._canvas.style["background-color"] = "#ffffff";
						}
						this._onResize();
						this._context = this._canvas.getContext("2d");
						this._context.clearRect(
							0,
							0,
							this._width,
							this._height
						);
						// 这里可以设置是否随着窗口的滚动而滚动
						window.addEventListener("resize", this._onResize);
						window.addEventListener("scroll", this._onScroll);
					} catch (e) {
						console.warn("Canvas Context Error: " + e.toString());
						return;
					}
					this._onDraw();
				},
				addRibbon: function () {
					let dir = Math.round(random(1, 9)) > 5 ? "right" : "left",
						stop = 1000,
						hide = 200,
						min = 0 - hide,
						max = this._width + hide,
						movex = 0,
						movey = 0,
						startx = dir === "right" ? min : max,
						starty = Math.round(random(0, this._height));
					if (/^(top|min)$/i.test(this._options.verticalPosition)) {
						starty = 0 + hide;
					} else if (
						/^(middle|center)$/i.test(
							this._options.verticalPosition
						)
					) {
						starty = this._height / 2;
					} else if (
						/^(bottom|max)$/i.test(this._options.verticalPosition)
					) {
						starty = this._height - hide;
					}
					let ribbon = [],
						point1 = new Point(startx, starty),
						point2 = new Point(startx, starty),
						point3 = null,
						color = Math.round(random(0, 360)),
						delay = 0;
					while (typeof Undefined === "undefined") {
						if (stop <= 0) break;
						stop--;
						movex = Math.round(
							(Math.random() * 1 - 0.2) *
								this._options.horizontalSpeed
						);
						movey = Math.round(
							(Math.random() * 1 - 0.5) * (this._height * 0.25)
						);
						point3 = new Point();
						point3.copy(point2);
						if (dir === "right") {
							point3.add(movex, movey);
							if (point2.x >= max) break;
						} else if (dir === "left") {
							point3.subtract(movex, movey);
							if (point2.x <= min) break;
						}
						ribbon.push({
							point1: new Point(point1.x, point1.y),
							point2: new Point(point2.x, point2.y),
							point3: point3,
							color: color,
							delay: delay,
							dir: dir,
							alpha: 0,
							phase: 0,
						});
						point1.copy(point2);
						point2.copy(point3);
						delay += 4;
						color += this._options.colorCycleSpeed;
					}
					this._ribbons.push(ribbon);
				},
				_drawRibbonSection: function (section) {
					if (section) {
						if (section.phase >= 1 && section.alpha <= 0) {
							return true;
						}
						if (section.delay <= 0) {
							section.phase += 0.02;
							section.alpha = Math.sin(section.phase) * 1;
							section.alpha =
								section.alpha <= 0 ? 0 : section.alpha;
							section.alpha =
								section.alpha >= 1 ? 1 : section.alpha;
							if (this._options.animateSections) {
								let mod =
									Math.sin(
										1 + (section.phase * Math.PI) / 2
									) * 0.1;
								if (section.dir === "right") {
									section.point1.add(mod, 0);
									section.point2.add(mod, 0);
									section.point3.add(mod, 0);
								} else {
									section.point1.subtract(mod, 0);
									section.point2.subtract(mod, 0);
									section.point3.subtract(mod, 0);
								}
								section.point1.add(0, mod);
								section.point2.add(0, mod);
								section.point3.add(0, mod);
							}
						} else {
							section.delay -= 0.5;
						}
						let s = this._options.colorSaturation,
							l = this._options.colorBrightness,
							c =
								"hsla(" +
								section.color +
								", " +
								s +
								", " +
								l +
								", " +
								section.alpha +
								" )";
						this._context.save();
						if (this._options.parallaxAmount !== 0) {
							this._context.translate(
								0,
								this._scroll * this._options.parallaxAmount
							);
						}
						this._context.beginPath();
						this._context.moveTo(
							section.point1.x,
							section.point1.y
						);
						this._context.lineTo(
							section.point2.x,
							section.point2.y
						);
						this._context.lineTo(
							section.point3.x,
							section.point3.y
						);
						this._context.fillStyle = c;
						this._context.fill();
						if (this._options.strokeSize > 0) {
							this._context.lineWidth = this._options.strokeSize;
							this._context.strokeStyle = c;
							this._context.lineCap = "round";
							this._context.stroke();
						}
						this._context.restore();
					}
					return false;
				},
				_onDraw: function () {
					for (let i = 0, t = this._ribbons.length; i < t; ++i) {
						if (!this._ribbons[i]) {
							this._ribbons.splice(i, 1);
						}
					}
					this._context.clearRect(0, 0, this._width, this._height);
					for (let a = 0; a < this._ribbons.length; ++a) {
						let ribbon = this._ribbons[a],
							numSections = ribbon.length,
							numDone = 0;
						for (let b = 0; b < numSections; ++b) {
							if (this._drawRibbonSection(ribbon[b])) {
								numDone++;
							}
						}
						if (numDone >= numSections) {
							this._ribbons[a] = null;
						}
					}
					if (this._ribbons.length < this._options.ribbonCount) {
						this.addRibbon();
					}
					requestAnimationFrame(this._onDraw);
				},
				_onResize: function (e) {
					let screen = screenInfo(e);
					this._width = screen.width;
					this._height = screen.height;
					if (this._canvas) {
						this._canvas.width = this._width;
						this._canvas.height = this._height;
						if (this._context) {
							this._context.globalAlpha =
								this._options.colorAlpha;
						}
					}
				},
				_onScroll: function (e) {
					let screen = screenInfo(e);
					this._scroll = screen.scrolly;
				},
			};
			new Factory();
		});
	},
};
</script>

<style scoped>
#myCanvas {
	position: absolute;
	left: 0%;
	top: 0%;
	z-index: -1;
}
</style>